Explain the following general order of basicity in aqueous solution:
R2NH > RNH2 > R3N > NH3
Two effects: inductive and the solvation effect determines the basicity of alkyl amines.
As the number of alkyl group (electron releasing group with +I effect) increases, making the amine more basic. So, in terms of inductive effect, increasing the number of R's should increase the basicity.
Solvation is present only in the conjugate acid, more the number of H present in the conjugate acid more the H-bonding and more the stabilisation. Therefore the R' increases, the number of H-s in the conjugate acid decreases, solvation decreases. Hence, basicity should decrease.
The inductive and solvation effect both works in opposite direction. Inductive effect dominates to make all three amines stronger bases than NH3.
While in R3N solvation effect dominates over the inductive effect.
